1. Field of the Invention
The present invention relates to a vehicle drive system particularly suitable for small vehicles of the type having driving wheels disposed on both left and right sides of the chassis frame.
2. Description of the Prior Art
Hitherto, the transmission system for vehicles of the kind described has an input section connected to the output shaft of an engine and an output section connected to both driving wheels through a differential gear, wherein the output section is composed of a V-belt type automatic transmission gear. This transmission gear, however, involves a problem that there is a serious reduction of the transmission efficiency due to a slip in the output section particularly under heavy load because the V-belt type automatic transmission must transmit excessive power.
In the vehicle of the kind described, the driving system for the driving wheels and the suspension of the driving wheels are independent of each other. It is quite advantageous from the view point of simplification and compacting of the whole system, for the driving system and the suspension to be constructed integrally by making common use of some of the elements or constituents.
In the vehicle of the kind described, a wheel driving axle is disposed between the pair of driving wheels and the transmission for transmitting the power of the engine disposed at the center of the axle. This transmission occupies a considerably large space. For this reason, there is a practical limit in the reduction of the size of the vehicle while preserving the necessary volume of the vehicle. However, a further reduction in the vehicle size will become possible by disposing the transmission outside of the chassis.
Usually the transmission case for the V-belt type transmission has a split-type construction composed of two parts formed by casting. These two parts are assembled together after assembling the transmission. In order to compensate for the reduction in the rigidity of the transmission case due to the split type construction, it is necessary to increase the wall thickness of the transmission case. This inevitably leads to an increased weight of the transmission as a whole.